The founder of the Khan Academy asks, "what if we were to separate the teaching and credentialing roles of universities?"

He continues the idea to say there would be "rigorous, internationally recognized assessments that measured your understanding in proficiency in various fields."

Those exist today.  Consider the technical, information systems, computer science field. A quick search reveals no less than 130+ tool or technology specific certifications for IT professionals.  These range from operating systems to cyber security to application specific credentials.  There are many more by profession including human resources, systems engineering, systems architecture, and program manager disciplines.  The Professional Engineer credential is another distinguished certification.

Students ask about Credentials
As a professor, I often get asked which credentials are best to get and I always respond with the undergraduate or graduate degree.  These teach us the discipline, the process, the knowledge, and often technique to approach problem solving.  The lessons learned in undergraduate (and graduate) programs have "staying" power - they stay with students long after the degree has been completed and credential received. 

Industry or Tool Specific Certifications
One of the issues I see with these assessments is they are specific to a tool or a version of a tool.  To demonstrate mastery of a specific tool, these credentials may be considered worthy, but would not replace an education.  Perhaps we have heard the term "paper MCSE", those individuals who have the credential, but are ineffective at their positions.  This post from 2005 is an example where the individual passed the exams, but observed "the only problem was that I didn't know squat."

Another problem is the tools change through subsequent releases, feature upgrades, mergers, and acquisitions.  If one mastered an operating system in 2001, the platform has undoubtedly changed 11 years later.

Complimentary Certifications and Traditional Education
There are high schools that teach traditional curriculum as well as IT certifications such as the Cisco CCNA and/or CISSP.  Some higher education institutions include courses or modules  that prepare students for certification exams.  Industry certifications can be used to bolster a career or improve technical skills and practitioner skills after a university degree program is completed.

To answer the first question, I'm not sure why one would separate teaching and credentialing.  I have not even addressed the complexities of exam bias and bias on the international scale. 

Will post more on this later including the important social aspect of learning and education.
/jd